Genetic variability and differentiation among polymorphic populations of the Antarctic genus Synoicum (Tunicata, Ascidiacea) from the South Shetland Islands.

WIERNES, P; SAHADE, R; TATIÁN, M; CHIAPPERO, M

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2013 p. 1 - 12

0722-4060

In Antarctica, ascidians are among the most conspicuous and abundant organisms in benthic ecosystems and many species present wide distribution patterns. Two similar forms of ascidians of the genus Synoicum were sampled along the South Shetland Islands, one greenish-yellow with elongated stalks, and other yellow-orange with shorter stalks and more rounded bodies. The taxonomic analyses indicated that the greenish-yellow form corresponded to the description of the species S. ostentor and the yellow-orange form to that of S. adareanum. However, molecular analyses using the cytochrome oxidase I gene did not detect clear differences at the interspecific level. Moreover, some degree of gene flow may be occurring, strongly suggesting that both morphotypes did not achieve a complete reproductive isolation yet, that they can still interbreed and therefore should be considered as a single species. Surprisingly these results are not in line with recent studies of Antarctic fauna using a similar approach, which show a trend finding cases of genetically distinguishable cryptic species showing almost no morphological differences